Heart valve regurgitation occurs when the heart valve does not close completely as a result of disease or injury. Pulmonary valve regurgitation has been shown to increase a patient's susceptibility to arrhythmias, sudden death and right ventricular dysfunction. Similarly, mitral regurgitation due to ischemic and degenerative (prolapse) disease has been shown to contribute to left ventricular dysfunction due to remodeling, and to left ventricular dilation, resulting in worsening of the mitral regurgitation. Currently, malfunctioning heart valves are usually replaced with biologic or mechanical prostheses through open-heart surgery with the attendant significant risk of death, stroke, infection, bleeding, and complications due to the use of general anesthesia and cardiopulmonary bypass. Such procedures also have significant potential for a long recovery period. However, for certain disease states, percutaneous alternatives have been used in place of open-heart surgery due to the lower morbidity and mortality. For instance, rheumatic mitral stenosis, a condition in which the mitral valve does not open properly, has been treated by inserting a balloon from the femoral vein to enlarge the mitral valve opening.
Based on the success of percutaneous balloon valvuplasty for mitral stenosis, investigators have explored other alternative methods to treat valvular heart disease without surgery. For example, Cribier et al. describe in a report entitled “Percutaneous Transcatheter Implantation of an Aortic Valve Prosthesis for Calcific Aortic Stenosis,” Circulation, Dec. 10, 2002, pages 3006-3008, a balloon-expandable stent to which a biologic valve prosthesis is sewn. This device is utilized to treat calcific aortic stenosis. In an article entitled “Percutaneous Insertion of the Pulmonary Valve,” Journal of the American College of Cardiology, Vol. 39, No. 10, May 15, 2002, pages 1664-1669, Bonhoeffer et al. describe a similar stent approach with a bovine venous (jugular) valve inserted to treat pulmonic valve disease. Others are developing repair techniques for mitral valve disease that involve placing a clip on the mitral leaflets (U.S. Pat. No. 6,629,534), cinching the mitral annulus from the coronary sinus (U.S. Pat. No. 6,537,314), or deploying an inflatable heart valve that is mechanically held in place (U.S. Pat. No. 5,554,185).
Norred (U.S. Pat. No. 6,482,228) discloses a percutaneous aortic valve replacement in which a heart valve prosthesis having ribs and a circular elastomeric canopy is folded for insertion into a catheter for delivery to the implantation region without surgery. Once in the ascending aorta, the body and leaflets of the heart valve prosthesis are opened like an umbrella by pulling on a central column of suture-like members. Hinge joints are used to create a miniature umbrella. However, the aortic valve prosthesis is anchored using a stent system that is extended in the ascending aorta to anchor the valve in the aortic channel above the biologic aortic valve. The suture-like members used to open the umbrella structure are deployed as part of the stent system. Such a design is not amenable to placement of the heart valve prosthesis at the location of the biologic valve.
Other stented heart valve prostheses are described in the art in which the anchoring system is a passive one that requires either balloon expandable stents or a self-expanding stent design. For example, such stented designs are described in U.S. Pat. No. 6,454,799, US 2002/0138138, U.S. Pat. Nos. 6,582,462, 6,458,153, 6,425,916, and 5,855,601. It will be appreciated that once these stented heart valve prostheses are deployed, they cannot be repositioned, refolded, or easily removed. Furthermore, the rigidity of the stent as it is deployed in calcified positions may allow for regurgitation around the outside of the stent, as has been seen in the early aortic valve deployments which utilize this design. It is also difficult to position these designs as one has to inflate a balloon in a moving column of blood while the heart is beating and one only gets one chance to accurately deploy it.
An additional difficulty occurs when deploying a stented heart valve in an annulus that is not thickened by calcium. The stent design lends itself slightly better to the aortic position where the height of the annulus has been increased and the width thickened by the presence of calcium in calcific aortic stenosis. However, when calcium is not present, as in other causes of aortic valve disease and in the mitral position, the stent may be difficult to anchor on the relatively thin annulus. Furthermore, the nature by which the stent folds on a balloon and then expands with plastic deformability limits the ratio of its initial to final size such that it will, by necessity, have a fairly large profile making percutaneous insertion via catheter more difficult in a valve annulus with a large diameter that has not been reduced by calcium deposition.
An improved heart valve prosthesis design is desired that utilizes a folding structure that allows a low profile for insertion via a catheter and a large profile once deployed but without use of a balloon or stent, thereby allowing a smaller to larger profile range. A heart valve prosthesis design is also desired that can be deployed, folded, removed, and then redeployed so as to increase the safety as well as the preciseness of the deployment. The present invention addresses these and other needs in the heart valve prosthesis art.